1. Field
The field relates to an organic light emitting display, and a method for driving the display, and more particular to an organic light emitting display, which controls luminance corresponding to the brightness of peripheral (or ambient) light by adjusting an emission time and gamma compensation and a method for driving the display.
2. Discussion of Related Technology
In a flat panel display, a number of pixels are arranged on a substrate in the matrix, and is referred to as ‘display region’. A scan line and a data line are connected to each pixel. A data signal is selectively applied to a pixel to display images.
Flat panel displays are classified into either an active matrix type or a passive matrix type according to construction. Since each pixel is selected and emits light according to resolution, contrast, and operation speed in the active matrix type display, the pixel array is the main current sink of the display.
Such a flat panel display has been used as a display device of a portable information terminal such as a personal computer, a portable telephone, a PDA (personal digital assistant) or a monitor for a variety of information devices. An LCD (liquid crystal display) using a liquid crystal panel, an organic light emitting display using an organic light emitting diode, and a PDP (plasma display panel) using a plasma panel have been known as examples of such a flat panel display.
Recently, various flat plate displays with reduced weight and volume when compared with cathode ray tubes (CRT) have been developed. In particular, an organic light emitting display device having excellent emission efficiency, luminance, viewing angle, and high speed response, has been used.
FIG. 1 is a view showing a conventional organic light emitting display. With reference to FIG. 1, the conventional organic light emitting display includes a pixel portion 10, a data driver 20, a scan driver 30, and a power supply unit 40.
A plurality of pixels 1 are arranged at the pixel portion 10. Each of the pixels 1 includes an organic light emitting diode (not shown). N scan lines S1, S2, S3, . . . , Sn−1, Sn, and m data lines D1, D2, Dm−1, and Dm are arranged in a column direction and a row direction at the pixel portion 10, respectively. The N scan lines S1, S2, S3, . . . , Sn−1, Sn transfer a scan signal, and the m data lines D1, D2, Dm−1, and Dm transfers a data signal. The N scan lines S1, S2, S3, . . . , Sn−1, Sn receives a voltage of a first power source ELVDD and is driven in response thereto, and the m data lines D1, D2, Dm−1, and Dm receive a voltage of a second power source ELVSS and is driven in response thereto. Accordingly, in the pixel portion 10, an organic light emitting diode emits light according to the scan signal, the data signal, the voltage of the first power source ELVDD, and the voltage of the second power source ELVSS in order to display images.
The data driver 20 applies a data signal to the pixel portion 10. The data driver 20 is connected to data lines D1, D2, . . . , Dm−1, Dm, and provides the data signal to the pixel portion 10.
The scan driver 30 sequentially outputs a scan signal. That is, the scan driver 30 is connected to the scan lines S1, S2, S3, . . . , Sn−1, Sn, and transfers the scan signal to each row of the pixel portion 10. The data signal from the data driver 20 is applied to each row of the pixel portion to which the scan signal is transferred to display images. When all rows are selected, one frame is completed.
The power supply unit 40 transfers the voltage of a first power source ELVDD and the voltage of a second power source ELVSS to the pixel portion 10, so that an electric current corresponding to the data signal flows through each pixel 10 according to a voltage difference between the first power source ELVDD and a second power source ELVSS. Here, the second power source ELVSS has a voltage less than that of the first power source ELVDD.
As mentioned above, in the conventional organic light emitting display, when images are displayed with a predetermined luminance in an environment of high levels of peripheral light, it is perceived as darker than it should be. Accordingly, a user perceives the images as being too dark. Alternatively, when luminance of the peripheral light is lower, the image is perceived as being too bright. Accordingly, when the peripheral light varies, it may be difficult to recognize images.
Furthermore, in the organic light emitting display, when high luminance is generated, a large electric current flows through the pixel portion 10. In contrast to this, when low luminance is generated, a small electric current flows through the pixel portion 10. When the high luminance is generated, a large electric current flows through the pixel portion 10, and a large load is subjected to the power supply unit 40. Consequently, there is demand for the power supply unit to have a high output capability.
In addition, when there are many regions generating high luminance, the contrast is reduced, thereby deteriorating image quality.
Summary of Certain Inventive Aspects